The general objective of this project is the development of methods for the exposure of details of enzymic reactions by use of the heavy-atom kinetic isotope effect. Specific objectives for the next budget period are: 1) Completion of experimental and theoretical modeling work on the C13 isotope effects on the decarboxylation of malonic acid in water solution; 2) Completion of reaction coordinate eigenvector and reactant complexity studies on a simplified model of the enzyme-catalized decomposition of a pentatomic substance: 3) Initiation of computational studies of kinetic isotope effects in bond forming reactions.